Parallel preparation of high fidelity probes in an array format

ABSTRACT

The present invention provides massively parallel oligonucleotide synthesis and purification for applications that utilize large collections of defined high-fidelity oligonucleotides (e.g., from about 10 1  to about 10 5  different sequences, generally between 25-160 bases in length).

FIELD OF THE INVENTION

The present invention relates generally to the fabrication of oligonucleotides such as probes and primers using oligonucleotide array technology. The present invention relates to massively parallel oligonucleotide synthesis and purification for applications that utilize large collections of defined high-fidelity oligonucleotides.

BACKGROUND OF THE INVENTION

PCR techniques are well-established and widely used across various segments of life-science research, diagnostics, etc. An increasingly important trend in the application of PCR is the ability to multiplex the reaction, which requires, in addition to the usual thermal cycling equipment and enzyme, sets of carefully designed oligonucleotide primers (or probes). Oligonucleotide primers are traditionally prepared by the solid-supported phosphoranidite approach, either on controlled-pore glass, polymeric support or membrane support.

Following oligonucleotide assembly, the support is typically treated with a deprotection reagent to remove protecting groups and to cleave the oligonucleotide from the support in a single step. Due to the high stepwise efficiency of the solid-supported phosphoramidite approach, it is often not necessary to rigorously purify short oligonucleotides (25-40 mers) destined for use as PCR primers. More often, simple ethanol precipitation or cartridge separation is used to “desalt” the primer and remove small molecular-weight components.

Although careful purification is atypical, some means of identity and purity confirmation (i.e., QC) are normally required and the collection of such data is considered good lab practice. Primer confirmation can usually be accomplished by high-throughput analytical techniques such as MALDI-TOF mass spectrometry and/or capillary gel electrophoresis. Conventional small-scale solid-supported oligonucleotide synthesis methods (flow-through column, membrane, 96-well plate) produce enough primer for thousands of PCR reactions.

SUMMARY OF THE INVENTION

Methods are provided for generating high numbers of oligonucleotides as probes and primers using oligonucleotide array technology to provide oligonucleotides, probes and primers.

In particular, methods are also provided for fabricating a plurality of oligonucleotides having free 3′-hydroxyl groups from a high density oligonucleotide array. In a preferred embodiment, synthesis is initiated with a reverse-orientation RNA monomer that contains an orthogonal 2′-OH protecting group. Following conventional 3′→5′ probe synthesis, the 2′-OH protecting group is removed to allow base-induced intramolecular transesterification. The transesterification reaction causes release of the synthesized probe with an authentic 3′-hydroxy functionality, while the 2′,3′-cyclic phosphate remains attached to the solid support.

Another disclosed method has the steps of providing a solid substrate; attaching a plurality of linkers to the substrate, each said linker having a cleavable moiety, wherein the cleavable moiety is activatable at a distinct set of conditions and wherein activation of the cleavable moiety disrupts the linker to allow release of anything joined to the linker at the site of the cleavable moiety, to provide a plurality of attached linkers; attaching a first monomer to at least one of said plurality of linkers to provide an attached first monomer; attaching a second monomer to a least one of said attached first monomers or said attached plurality of linkers to provide an attached second monomer; attaching a third monomers to a least one of said attached first monomer, second monomers or plurality of linkers to provide an attached third monomer; repeating said step of attaching a monomer until the desired array of polymers is complete and subjecting the array to the distinct set of conditions to provide release of polymers from the array.

DESCRIPTION OF THE DRAWINGS

“FIG. 1” depicts the transesterification reaction causing release of the synthesized probe with an authentic 3′-hydroxy functionality, while the 2′,3′-cyclic phosphate remains attached to the solid support.

“FIG. 2” shows two exemplary monomers used in the process depicted in FIG. 1.

“FIG. 3” depicts a purification scheme to obtain full length probes with authentic termi.

DETAILED DESCRIPTION OF THE INVENTION

A. General

The present invention has many preferred embodiments and relies on many patents, applications and other references for details known to those of the art. Therefore, when a patent, application, or other reference is cited or repeated below, it should be understood that it is incorporated by reference in its entirety for all purposes as well as for the proposition that is recited.

As used in this application, the singular form “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “an agent” includes a plurality of agents, including mixtures thereof.

An individual is not limited to a human being but may also be other organisms including but not limited to mammals, plants, bacteria, or cells derived from any of the above.

Throughout this disclosure, various aspects of this invention can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

The practice of the present invention may employ, unless otherwise indicated, conventional techniques and descriptions of organic chemistry, polymer technology, molecular biology (including recombinant techniques), cell biology, biochemistry, and immunology, which are within the skill of the art. Such conventional techniques include polymer array synthesis, hybridization, ligation, and detection of hybridization using a label. Specific illustrations of suitable techniques can be had by reference to the example herein below. However, other equivalent conventional procedures can, of course, also be used. Such conventional techniques and descriptions can be found in standard laboratory manuals such as Genome Analysis: A Laboratory Manual Series (Vols. I-IV), Using Antibodies: A Laboratory Manual, Cells: A Laboratory Manual, PCR Primer: A Laboratory Manual, and Molecular Cloning: A Laboratory Manual (all from Cold Spring Harbor Laboratory Press), Stryer, L. (1995) Biochemistry (4th Ed.) Freeman, New York, Gait, “Oligonucleotide Synthesis: A Practical Approach” 1984, IRL Press, London, Nelson and Cox (2000), Lehninger, Principles of Biochemistry 3^(rd) Ed., W.H. Freeman Pub., New York, N.Y. and Berg et al. (2002) Biochemistry, 5^(th) Ed., W.H. Freeman Pub., New York, N.Y., all of which are herein incorporated in their entirety by reference for all purposes.

The present invention can employ solid substrates, including arrays in some preferred embodiments. Methods and techniques applicable to polymer (including protein) array synthesis have been described in U.S. Ser. No. 09/536,841, WO 00/58516, U.S. Pat. Nos. 5,143,854, 5,242,974, 5,252,743, 5,324,633, 5,384,261, 5,405,783, 5,424,186, 5,451,683, 5,482,867, 5,491,074, 5,527,681, 5,550,215, 5,571,639, 5,578,832, 5,593,839, 5,599,695, 5,624,711, 5,631,734, 5,795,716, 5,831,070, 5,837,832, 5,856,101, 5,858,659, 5,936,324, 5,968,740, 5,974,164, 5,981,185, 5,981,956, 6,025,601, 6,033,860, 6,040,193, 6,090,555, 6,136,269, 6,269,846 and 6,428,752, in PCT Applications Nos. PCT/US99/00730 (International Publication No. WO 99/36760) and PCT/US01/04285 (International Publication No. WO 01/58593), which are all incorporated herein by reference in their entirety for all purposes.

Patents that describe synthesis techniques in specific embodiments include U.S. Pat. Nos. 5,412,087, 6,147,205, 6,262,216, 6,310,189, 5,889,165, and 5,959,098. Nucleic acid arrays are described in many of the above patents, but the same techniques are applied to polypeptide arrays.

Nucleic acid arrays that are useful in the present invention include those that are commercially available from Affymetrix (Santa Clara, Calif.) under the brand name GeneChip®. Example arrays are shown on the website at affymetrix.com.

The present invention also contemplates many uses for polymers attached to solid substrates. These uses include gene expression monitoring, profiling, library screening, genotyping and diagnostics. Gene expression monitoring and profiling methods can be shown in U.S. Pat. Nos. 5,800,992, 6,013,449, 6,020,135, 6,033,860, 6,040,138, 6,177,248 and 6,309,822. Genotyping and uses therefore are shown in U.S. Ser. Nos. 10/442,021, 10/013,598 (U.S. Patent Application Publication 20030036069), and U.S. Pat. Nos. 5,856,092, 6,300,063, 5,858,659, 6,284,460, 6,361,947, 6,368,799 and 6,333,179. Other uses are embodied in U.S. Pat. Nos. 5,871,928, 5,902,723, 6,045,996, 5,541,061, and 6,197,506.

The present invention also contemplates sample preparation methods in certain preferred embodiments. Prior to or concurrent with genotyping, the genomic sample may be amplified by a variety of mechanisms, some of which may employ PCR. See, for example, PCR Technology: Principles and Applications for DNA Amplification (Ed. H. A. Erlich, Freeman Press, NY, N.Y., 1992); PCR Protocols: A Guide to Methods and Applications (Eds. Innis, et al., Academic Press, San Diego, Calif., 1990); Mattila et al., Nucleic Acids Res. 19, 4967 (1991); Eckert et al., PCR Methods and Applications 1, 17 (1991); PCR (Eds. McPherson et al., IRL Press, Oxford); and U.S. Pat. Nos. 4,683,202, 4,683,195, 4,800,159, 4,965,188, and 5,333,675, and each of which is incorporated herein by reference in their entireties for all purposes. The sample may be amplified on the array. See, for example, U.S. Pat. No. 6,300,070 and U.S. Ser. No. 09/513,300, which are incorporated herein by reference.

Other suitable amplification methods include the ligase chain reaction (LCR) (for example, Wu and Wallace, Genomics 4, 560 (1989), Landegren et al., Science 241, 1077 (1988) and Barringer et al. Gene 89:117 (1990)), transcription amplification (Kwoh et al., Proc. Natl. Acad. Sci. USA 86, 1173 (1989) and WO88/10315), self-sustained sequence replication (Guatelli et al., Proc. Nat. Acad. Sci. USA, 87, 1874 (1990) and WO90/06995), selective amplification of target polynucleotide sequences (U.S. Pat. No. 6,410,276), consensus sequence primed polymerase chain reaction (CP-PCR) (U.S. Pat. No. 4,437,975), arbitrarily primed polymerase chain reaction (AP-PCR) (U.S. Pat. Nos. 5,413,909, 5,861,245) and nucleic acid based sequence amplification (NABSA). (See, U.S. Pat. Nos. 5,409,818, 5,554,517, and 6,063,603, each of which is incorporated herein by reference). Other amplification methods that may be used are described in, U.S. Pat. Nos. 5,242,794, 5,494,810, 4,988,617 and in U.S. Ser. No. 09/854,317, each of which is incorporated herein by reference.

Additional methods of sample preparation and techniques for reducing the complexity of a nucleic sample are described in Dong et al., Genome Research 11, 1418 (2001), in U.S. Pat. Nos. 6,361,947, 6,391,592 and U.S. Ser. Nos. 09/916,135, 09/920,491 (U.S. Patent Application Publication 20030096235), 09/910,292 (U.S. Patent Application Publication 20030082543), and 10/013,598.

Methods for conducting polynucleotide hybridization assays have been well developed in the art. Hybridization assay procedures and conditions will vary depending on the application and are selected in accordance with the general binding methods known including those referred to in: Maniatis et al. Molecular Cloning: A Laboratory Manual (2^(nd) Ed. Cold Spring Harbor, N.Y, 1989); Berger and Kimmel Methods in Enzymology, Vol. 152, Guide to Molecular Cloning Techniques (Academic Press, Inc., San Diego, Calif., 1987); Young and Davism, P.N.A.S, 80: 1194 (1983). Methods and apparatus for carrying out repeated and controlled hybridization reactions have been described in U.S. Pat. Nos. 5,871,928, 5,874,219, 6,045,996 and 6,386,749, 6,391,623 each of which are incorporated herein by reference

The present invention also contemplates signal detection of hybridization between ligands in certain preferred embodiments. See U.S. Pat. Nos. 5,143,854, 5,578,832; 5,631,734; 5,834,758; 5,936,324; 5,981,956; 6,025,601; 6,141,096; 6,185,030; 6,201,639; 6,218,803; and 6,225,625, in U.S. Ser. No. 10/389,194 and in PCT Application PCT/US99/06097 (published as WO99/47964), each of which also is hereby incorporated by reference in its entirety for all purposes.

Methods and apparatus for signal detection and processing of intensity data are disclosed in, for example, U.S. Pat. Nos. 5,143,854, 5,547,839, 5,578,832, 5,631,734, 5,800,992, 5,834,758; 5,856,092, 5,902,723, 5,936,324, 5,981,956, 6,025,601, 6,090,555, 6,141,096, 6,185,030, 6,201,639; 6,218,803; and 6,225,625, in U.S. Ser. Nos. 10/389,194, 60/493,495 and in PCT Application PCT/US99/06097 (published as WO99/47964), each of which also is hereby incorporated by reference in its entirety for all purposes.

The practice of the present invention may also employ conventional biology methods, software and systems. Computer software products of the invention typically include computer readable medium having computer-executable instructions for performing the logic steps of the method of the invention. Suitable computer readable medium include floppy disk, CD-ROM/DVD/DVD-ROM, hard-disk drive, flash memory, ROM/RAM, magnetic tapes and etc. The computer executable instructions may be written in a suitable computer language or combination of several languages. Basic computational biology methods are described in, for example Setubal and Meidanis et al., Introduction to Computational Biology Methods (PWS Publishing Company, Boston, 1997); Salzberg, Searles, Kasif, (Ed.), Computational Methods in Molecular Biology, (Elsevier, Amsterdam, 1998); Rashidi and Buehler, Bioinformatics Basics: Application in Biological Science and Medicine (CRC Press, London, 2000) and Ouelette and Bzevanis Bioinformatics: A Practical Guide for Analysis of Gene and Proteins (Wiley & Sons, Inc., 2^(nd) ed., 2001). See U.S. Pat. No. 6,420,108.

The present invention may also make use of various computer program products and software for a variety of purposes, such as probe design, management of data, analysis, and instrument operation. See, U.S. Pat. Nos. 5,593,839, 5,795,716, 5,733,729, 5,974,164, 6,066,454, 6,090,555, 6,185,561, 6,188,783, 6,223,127, 6,229,911 and 6,308,170.

Additionally, the present invention may have preferred embodiments that include methods for providing genetic information over networks such as the Internet as shown in U.S. Ser. Nos. 10/197,621, 10/063,559 (United States Publication No. 20020183936), 10/065,856, 10/065,868, 10/328,818, 10/328,872, 10/423,403, and 60/482,389.

b) Definitions

An “array” represents an intentionally created collection of molecules which can be prepared either synthetically or biosynthetically. In particular, the term “array” herein means an intentionally created collection of probes (as used herein typically polymers, peptides, polynucleotides and or oligonucleotides) attached to at least a first surface of at least one solid support wherein the identity of each polynucleotide at a given predefined region or positionally defined location is known. The terms “array,” “biological chip” and “chip” are used interchangeably. A polymer array also can include only a subset of the complete set of probes. Similarly, a given array can exist on more than one separate substrate, e.g., where the number of sequences necessitates a larger surface area or more than one solid substrate in order to include all of the desired oligonucleotide sequences.

“Solid support,” “support,” and “substrate” refer to a material or group of materials having a rigid or semi-rigid surface or surfaces. In many embodiments, at least one surface of the solid support will be substantially flat, although in some embodiments it may be desirable to physically separate synthesis regions for different compounds with, for example, wells, raised regions, pins, etched trenches, or the like. According to other embodiments, the solid support(s) will take the form of beads, resins, gels, microspheres, fibers or other geometric configurations.

The phrase “coupled to a support” means bound directly or indirectly thereto including attachment by covalent binding, hydrogen bonding, ionic interaction, hydrophobic interaction, or otherwise.

“Nucleotide” and “ribonucleotide” refers to both naturally occurring and non-naturally occurring compounds having a heterocyclic base, a sugar, and a linking group, preferably a phosphate ester. For example, structural groups may be added to the ribosyl or deoxyribosyl unit of the nucleotide, such as a methyl or allyl group at the 2′-O position or a fluoro group that substitutes for the 2′-O group. The linking group, such as a phosphodiester, of the nucleic acid may be substituted or modified, for example with methyl phosphonates or O-methyl phosphates. Bases and sugars can also be modified, as is known in the art. For example, unless otherwise limited the phrase would also cover synthetic and naturally occurring variants of nucleic acids, including without limitation, base variants such as 7-deazapurine, 8-aza-7-deazapurine, isocytosine, pseudo isocytosine, and isouracil.

The terms “nucleic acid” or “nucleic acid molecule” as used herein refer to a deoxyribonucleotide or ribonucleotide (see above) polymer in either single or double stranded form. These terms also encompass DNA-RNA hybrids.

The term “sugar” as used herein relates to monosaccharide moieties. Preferred sugars are in cyclic form, for example, in furanose (5-membered ring) or pyranose (6-membered ring) forms. Sugars may be in any of their enantiomeric, diasteriomeric or stereoisomeric forms.

As used herein, the terms “oligonucleotide” and “polynucleotide” are used interchangeably in the conventional sense to refer to molecules comprising two or more nucleosides, each nucleoside being linked to at least one other nucleoside by an internucleoside linkage. The oligonucleotides of the present invention may be linear, branched, or cyclic, but are preferably linear.

The term “mature oligonucleotide” or “full length oligonucleotide” refers to an oligonucleotide which has successfully undergone each of its coupling reactions so that its sequence is complete and as expected per the synthetic scheme.

The term “prematurely terminated” or “truncated” refers to an oligonucleotide which has failed at one or more coupling reactions so that its sequence lacks specific units intended per the synthetic scheme.

The term “reactive functional groups” refers to functional groups which may react with other available functional groups under specified conditions to yield a covalent linkage. Examples of preferred reactive functional groups are hydroxyl (i.e., —OH) and phosphoramidite (i.e., —OP(OR′)NR₂ wherein R′ and R are organic groups comprising 1 to 20 carbon atoms). A preferred group of phosphoramidite functional groups are those for which R′ is —CH₃, —CH₂CH₃, —CH₂CH₂ CN, or —C₆H₄Cl; and R is —CH(CH₃)₂.

The term “protected” or “otherwise unreactive” functional groups refers to functional groups which are essentially unreactive toward other available functional groups under specified conditions. The term “functional group protection” is used herein in the conventional chemical sense to refer to common chemical methods employed to reversibly render unreactive a functional group, which otherwise would be reactive, under specified conditions (such as pH, temperature, radiation, solvent, and the like). A wide variety of such “protecting”, “blocking”, or “masking” methods are widely used and well known in organic synthesis. For example, a compound which has two non-equivalent reactive functional groups, both of which would be reactive under specified conditions, may be derivatized to render one of the functional groups “protected”, and therefore unreactive, under the specified conditions; so protected, the compound may be used as a reactant which has effectively only one reactive functional group. After the desired reaction (involving the reactive functional group) is complete, the protected group may be “deprotected” to return it to its original functionality.

A wide variety of protecting group strategies are known. For example, hydroxyl groups (i.e., —OH) which are reactive toward a certain other functional groups (for example, phosphoramidite) under alkaline conditions might be “protected” by conversion to a suitable ether, which is unreactive under alkaline conditions. When it is desired to “deprotect” the hydroxyl group, the protected compound might be treated with acid. For example, an —OH group may be protected by reaction with DMT-Cl to yield the acid-labile —ODMT group which may be deprotected, for example, by treatment with a suitable acid, such as dichloroacetic acid.

Methods of obtaining nucleic acid sequences of a given length and known sequence are known to those of skill in the art. Methods of solid phase oligonucleotide synthesis are described in, for example: Advances in the Synthesis of Oligonucleotides by the Phosphoramidite Approach, Beaucage, S. L.; Iyer, R. P., Tetrahedron, 1992, 48, 2223-2311; U.S. Pat. Nos. 4,58,066; 4,500,707; 5,132,418; 4,973,679; 4,415,732; Re. 34,069; and 5,026,838.

The term “linker” means a molecule or group of molecules attached to a substrate and spacing a synthesized polymer from the substrate for exposure/binding to a receptor.

The term “activation energy wavelength” refers to that wavelength of electromagnetic radiation that will activate a photoprotective group or photocleavable group.

The term “activator” refers to a compound that facilitates coupling of one nucleic acid to another, preferably in 3′-position of one nucleic acid to 5′-position of the other nucleic acid or vice a versa.

The terms “quality,” “performance” and “intensity” are used interchangeably herein when referring to oligonucleotide probes or binding of a target molecule to oligonucleotide probes mean sensitivity of oligonucleotide probes to bind to a target molecule while giving a minimum of false signals.

The term “wafer” generally refers to a substantially flat sample of substrate (i.e., solid-support) from which a plurality of individual arrays or chips can be fabricated.

The term “functional group” means a reactive chemical moiety present on a given monomer, polymer, linker or substrate surface. Examples of functional groups include, e.g., the 3′ and 5′ hydroxyl groups of nucleotides and nucleosides, as well as the reactive groups on the nucleobases of the nucleic acid monomers, e.g., the exocyclic amine group of guanosine, as well as amino and carboxyl groups on amino acid monomers.

The term photoprotecting group (also called photolabile protecting groups or photogroup for short) means a material which is chemically bound to a reactive functional group on a monomer unit, linker, or polymer and which may be removed upon selective exposure to electromagnetic radiation or light, especially ultraviolet and visible light.

The term “reactive group” refers to a group that allows a covalent reaction to occur between for example a monomer and a linker or between a second monomer and a first attached monomer. A reactive group may be protected by photoprotective removable group. Removal of the photogroup, yields a deprotected reactive group. The terms “array” and “chip” are used interchangeably herein and refer to the final product of the individual array of nucleic acid or oligonucleotide sequences, having a plurality of positionally distinct oligonucleotide sequences coupled to the surface of the substrate. “Array” is used with reference to nucleic acid or oligonucleotide, but it should be appreciated that either can be-attached to a solid support. Reference will be made to oligonucleotide arrays as a preferred example of the present invention.

The term “alkyl” refers to a branched or straight chain acyclic, monovalent saturated hydrocarbon radical of one to twenty carbon atoms. The term “alkenyl” refers to an unsaturated hydrocarbon radical which contains at least one carbon-carbon double bond and includes straight chain, branched chain and cyclic radicals.

The term “alkynyl” refers to an unsaturated hydrocarbon radical which contains at least one carbon-carbon triple bond and includes straight chain, branched chain and cyclic radicals.

The term “aryl” refers to an aromatic monovalent carboxylic radical having a single ring (e.g., phenyl) or two condensed rings (e.g., naphthyl), which can optionally be mono-, di-, or tri-substituted, independently, with alkyl, lower-alkyl, cycloalkyl, ydroxylower-alkyl, aminoloweralkyl, hydroxyl, thiol, amino, halo, nitro, lower-alkylthio, lower-alkoxy, mono-lower-alkylamino, di-lower-alkylamino, acyl, hydroxycarbonyl, lower-alkoxycarbonyl, hydroxysulfonyl, lower-alkoxysulfonyl, lower-alkylsulfonyl, lower-alkylsulfinyl, trifluoromethyl, cyano, tetrazoyl, carbamoyl, lower-alkylcarbamoyl, and di-lower-alkylcarbamoyl.

Alternatively, two adjacent positions of the aromatic ring may be substituted with a methylenedioxy or ethylenedioxy group. The term “heteroaromatic” refers to an aromatic monovalent mono- or poly-cyclic radical having at least one heteroatom within the ring, e.g., nitrogen, oxygen or sulfur, wherein the aromatic ring can optionally be mono-, di- or tri-substituted, independently, with alkyl, lower-alkyl, cycloalkyl, hydroxylower-alkyl, aminolower-alkyl, hydroxyl, thiol, amino, halo, nitro, lower-alkylthio, loweralkoxy, mono-lower-alkylamino, di-lower-alkylamino, acyl, hydroxycarbonyl, lower-alkoxycarbonyl, hydroxysulfonyl, lower-alkoxysulfonyl, lower-alkylsulfonyl, lower-alkylsulfinyl, trifluoromethyl, cyano, tetrazoyl, carbamoyl, loweralkylcarbamoyl, and di-lower-alkylcarbamoyl. For example, typical heteroaryl groups with one or more nitrogen atoms are tetrazoyl, pyridyl (e.g., 4-pyridyl, 3-pyridyl, 2-pyridyl), pyrrolyl (e.g., 2-pyrrolyl, 2-(N-alkyl)pyrrolyl), pyridazinyl, quinolyl (e.g. 2-quinolyl, 3-quinolyl etc.), imidazolyl, isoquinolyl, pyrazolyl, pyrazinyl, pyrimidinyl, pyridonyl or pyridazinonyl; typical oxygen heteroaryl radicals with an oxygen atom are 2-furyl, 3-furyl or benzofuranyl; typical sulfur heteroaryl radicals are thienyl, and benzothienyl; typical mixed heteroatom heteroaryl radicals are furazanyl and phenothiazinyl.

Further the term also includes instances where a heteroatom within the ring has been oxidized, such as, for example, to form an N-oxide or sulfone. The term “optionally substituted” refers to the presence or lack thereof of a substituent on the group being defined. When substitution is present the group may be mono-, di- or tri-substituted, independently, with alkyl, lower-alkyl, cycloalkyl, hydroxylower-alkyl, aminoloweralkyl, hydroxyl, thiol, amino, halo, nitro, lower-alkylthio, lower-alkoxy, mono-lower-alkylamino, di-lower-alkylamino, acyl, hydroxycarbonyl, lower-alkoxycarbonyl, hydroxysulfonyl, lower-alkoxysulfonyl, lower-alkylsulfonyl, lower-alkylsulfinyl, trifluoromethyl, cyano, tetrazoyl, carbamoyl, lower-alkylcarbamoyl, and di-lower-alkylcarbamoyl. Typically, electron-donating substituents such as alkyl, lower-alkyl, cycloalkyl, hydroxylower-alkyl, aminolower-alkyl, hydroxyl, thiol, amino, halo, lower-alkylthio, lower-alkoxy, mono-lower-alkylamino and di-lower-alkylamino are preferred.

The term “electron donating group” refers to a radical group that has a lesser affinity for electrons than a hydrogen atom would if it occupied the same position in the molecule. For example, typical electron donating groups are hydroxy, alkoxy (e.g. methoxy), amino, alkylamino and dialkylamine.

The term “leaving group” means a group capable of being displaced by a nucleophile in a chemical reaction, for example halo, nitrophenoxy, pentafluorophenoxy, alkyl sulfonates (e.g., methanesulfonate), aryl sulfonates, phosphates, sulfonic acid, sulfonic acid salts, and the like.

“Activating group” refers to those groups which, when attached to a particular functional group or reactive site, render that site more reactive toward covalent bond formation with a second functional group or reactive site. The group of activating groups which are useful for a carboxylic acid include simple ester groups and anhydrides. The ester groups include alkyl, aryl and alkenyl esters and in particular such groups as 4-nitrophenyl, N-hydroxylsuccinimide and pentafluorophenol. Other activating groups are known to those of skill in the art.

A “cleavable moiety” or “releasable group” refers to a molecule which can be cleaved or released under a set of distinct conditions, e.g., certain wave lengths of light or certain chemical conditions. As employed in the context of the present invention of arrays of releasable polymer the conditions much be such as not to substantially damage or harm the polymer in questions. Persons of skill in the art will recognize what cleavable moiety may be employed for example where the polymer is a nucleic acid or a peptide.

“Predefined region” refers to a localized area on a solid support. It can be where synthesis takes place or where a nucleic acid is placed. Predefined region can also be defined as a “selected region.” The predefined region may have any convenient shape, e.g., circular, rectangular, elliptical, wedge-shaped, etc. For the sake of brevity herein, “predefined regions” are sometimes referred to simply as “regions.” In some embodiments, a predefined region and, therefore, the area upon which each distinct compound is synthesized or placed is smaller than about 1 cm2 or less than 1 mm2. Within these regions, the molecule therein is preferably in a substantially pure form. In additional embodiments, a predefined region can be achieved by physically separating the regions (i.e., beads, resins, gels, etc.) into wells, trays, etc.

A “linker” is a molecule or group of molecules attached to a substrate and spacing a synthesized polymer from the substrate for exposure binding to a receptor.

A “channel block” is a material having a plurality of grooves or recessed regions on a surface thereof. The grooves or recessed regions may take on a variety of geometric configurations, including but not limited to stripes, circles, serpentine paths, or the like. Channel blocks may be prepared in a variety of manners, including etching silicon blocks, molding or pressing polymers, etc.

A “monomer” is a member of the set of small molecules which can be joined together to form a polymer. The set of monomers includes but is not restricted to, for example, the set of common L-amino acids, the set of common D-amino acids, the set of synthetic amino acids, the set of nucleotides and the set of pentoses and hexoses. As used herein, monomer refers to any member of a basis set for synthesis of a polymer. Thus, monomers refers to dimmers, trimers, tetramers and higher units of molecules which can be joined to form a polymer. For example, dimmers of the 20 naturally occurring L-amino acids for a basis set of 400 monomers for synthesis of polypeptides. Different basis sets of monomers may be used at successive steps in the synthesis of a polymer. Furthermore, each of the sets may include protected members which are modified after synthesis.

A “polymer” is composed of two or more joined monomers and includes for example both linear and cyclic polymers of nucleic acids, polysaccharides, phospholipids, and peptides having either a-, 0-, and o-amino acids, hetero-polymers in which a known drug is covalently bound to any of the above, polyurethanes, polyesters, polycarbonates, polyureas, polyamides, polyethyleneimines, polyarylene sulfides, polysiloxanes, polyimides, polyacetates, or other polymers.

A “releasable group” is a moiety or chemical group which is labile, i.e., may be activated or cleaved, under a given set of conditions, but is stable under other sets of conditions.

The term “monomer” as used herein refers to a single unit of polymer, which can be linked with the same or other monomers to form a biopolymer (for example, a single amino acid or nucleotide with two linking groups one or both of which may have removable protecting groups) or a single unit which is not part of a biopolymer. Thus, for example, a nucleotide is a monomer within an oligonucleotide polymer, and an amino acid is a monomer within a protein or peptide polymer; antibodies, antibody fragments, chromosomes, plasmids, mRNA, cRNA, tRNA etc., for example, are also polymers.

The term “biopolymer” or sometimes refer by “biological polymer” as used herein is intended to mean repeating units of biological or chemical moieties. Representative biopolymers include, but are not limited to, nucleic acids, oligonucleotides, amino acids, proteins, peptides, hormones, oligosaccharides, lipids, glycolipids, lipopolysaccharides, phospholipids, synthetic analogues of the foregoing, including, but not limited to, inverted nucleotides, peptide nucleic acids, Meta-DNA, and combinations of the above. It is important to note that biopolymers and polymers are not mutually exclusive. Proteins, enzymes, DNA, polyethylene, RNA, are all polymers as they are derived from a repeating monomer units. However, proteins, enzymes, DNA are all biopolymers as many of them first appeared in nature. Sometimes, it is not easy to classify something as a biopolymer or a polymer. For example, vast number of human made amino acid derivatives and nucleotide derivatives have been created and polymerized. Some of these are based on natural products, many more are not. At this point the distinction between the two can be somewhat semantical.

The term “biopolymer synthesis” as used herein is intended to encompass the synthetic production, both in situ (in the cell) and synthetically, e.g. by organic synthetic techniques outside of the cell, of a biopolymer. Related to a biopolymer is a “biomonomer”.

The term “combinatorial synthesis strategy” as used herein refers to a combinatorial synthesis strategy is an ordered strategy for parallel synthesis of diverse polymer sequences by sequential addition of reagents which may be represented by a reactant matrix and a switch matrix, the product of which is a product matrix. A reactant matrix is a 1 column by m row matrix of the building blocks to be added. The switch matrix is all or a subset of the binary numbers, preferably ordered, between 1 and m arranged in columns. A “binary strategy” is one in which at least two successive steps illuminate a portion, often half, of a region of interest on the substrate. In a binary synthesis strategy, all possible compounds which can be formed from an ordered set of reactants are formed. In most preferred embodiments, binary synthesis refers to a synthesis strategy which also factors a previous addition step. For example, a strategy in which a switch matrix for a masking strategy halves regions that were previously illuminated, illuminating about half of the previously illuminated region and protecting the remaining half (while also protecting about half of previously protected regions and illuminating about half of previously protected regions). It will be recognized that binary rounds may be interspersed with non-binary rounds and that only a portion of a substrate may be subjected to a binary scheme. A combinatorial “masking” strategy is a synthesis which uses light or other spatially selective deprotecting or activating agents to remove protecting groups from materials for addition of other materials such as amino acids.

The term “complementary” as used herein refers to the hybridization or base pairing between nucleotides or nucleic acids, such as, for instance, between the two strands of a double stranded DNA molecule or between an oligonucleotide primer and a primer binding site on a single stranded nucleic acid to be sequenced or amplified. Complementary nucleotides are, generally, A and T (or A and U), or C and G. Two single stranded RNA or DNA molecules are said to be complementary when the nucleotides of one strand, optimally aligned and compared and with appropriate nucleotide insertions or deletions, pair with at least about 80% of the nucleotides of the other strand, usually at least about 90% to 95%, and more preferably from about 98 to 100%. Alternatively, complementarity exists when an RNA or DNA strand will hybridize under selective hybridization conditions to its complement. Typically, selective hybridization will occur when there is at least about 65% complementary over a stretch of at least 14 to 25 nucleotides, preferably at least about 75%, more preferably at least about 90% complementary. See, M. Kanehisa Nucleic Acids Res. 12:203 (1984), incorporated herein by reference.

The term “copolymer” refers to a polymer that is composed of more than one monomer. Copolymers may be prepared by polymerizing one or more monomers to provide a copolymer.

The term “detectable moiety” means a chemical group that provides a signal. The signal is detectable by any suitable means, including spectroscopic, photochemical, biochemical, immunochemical, electrical, optical or chemical means. In certain cases, the signal is detectable by 2 or more means.

The detectable moiety provides the signal either directly or indirectly. A direct signal is produced where the labeling group spontaneously emits a signal, or generates a signal upon the introduction of a suitable stimulus. Radiolabels, such as ³H, ¹²⁵I, ³⁵S, ¹⁴C or ³²P, and magnetic particles, such as Dynabeads™, are nonlimiting examples of groups that directly and spontaneously provide a signal. Labeling groups that directly provide a signal in the presence of a stimulus include the following nonlimiting examples: colloidal gold (40-80 nm diameter), which scatters green light with high efficiency; fluorescent labels, such as fluorescein, Texas red, Rhoda mine, and green fluorescent protein (Molecular Probes, Eugene, Oreg.), which absorb and subsequently emit light; chemiluminescent or bioluminescent labels, such as luminol, lophine, acridine salts and luciferins, which are electronically excited as the result of a chemical or biological reaction and subsequently emit light; spin labels, such as vanadium, copper, iron, manganese and nitroxide free radicals, which are detected by electron spin resonance (ESR) spectroscopy; dyes, such as quinoline dyes, triarylmethane dyes and acridine dyes, which absorb specific wavelengths of light; and colored glass or plastic (e.g., polystyrene, polypropylene, latex, etc.) beads. See U.S. Pat. Nos. 3,817,837; 3,850,752; 3,939,350; 3,996,345; 4,277,437; 4,275,149 and 4,366,241.

A detectable moiety provides an indirect signal where it interacts with a second compound that spontaneously emits a signal, or generates a signal upon the introduction of a suitable stimulus. Biotin, for example, produces a signal by forming a conjugate with streptavidin, which is then detected. See Hybridization With Nucleic Acid Probes. In Laboratory Techniques in Biochemistry and Molecular Biology; Tijssen, P., Ed.; Elsevier: New York, 1993; Vol. 24. An enzyme, such as horseradish peroxidase or alkaline phosphatase, that is attached to an antibody in a label-antibody-antibody as in an ELISA assay, also produces an indirect signal.

A preferred detectable moiety is a fluorescent group. Fluorescent groups typically produce a high signal to noise ratio, thereby providing increased resolution and sensitivity in a detection procedure. Preferably, the fluorescent group absorbs light with a wavelength above about 300 nm, more preferably above about 350 nm, and most preferably above about 400 nm. The wavelength of the light emitted by the fluorescent group is preferably above about 310 nm, more preferably above about 360 nm, and most preferably above about 410 nm.

The fluorescent detectable moiety is selected from a variety of structural classes, including the following nonlimiting examples: 1- and 2-aminonaphthalene, p,p′ diaminostilbenes, pyrenes, quaternary phenanthridine salts, 9-aminoacridines, p,p′-diaminobenzophenone imines, anthracenes, oxacarbocyanine, marocyanine, 3-aminoequilenin, perylene, bisbenzoxazole, bis-p-oxazolyl benzene, 1,2-benzophenazin, retinol, bis-3-aminopridinium salts, hellebrigenin, tetracycline, sterophenol, benzimidazolyl phenylamine, 2-oxo-3-chromen, indole, xanthen, 7-hydroxycoumarin, phenoxazine, salicylate, strophanthidin, porphyrins, triarylmethanes, flavin, xanthene dyes (e.g., fluorescein and rhodamine dyes); cyanine dyes; 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene dyes and fluorescent proteins (e.g., green fluorescent protein, phycobiliprotein).

A number of fluorescent compounds are suitable for incorporation into the present invention. Nonlimiting examples of such compounds include the following: dansyl chloride; fluoresceins, such as 3,6-dihydroxy-9-phenylxanthhydrol; rhodamineisothiocyanate; N-phenyl-1-amino-8-sulfonatonaphthalene; N-phenyl-2-amino-6-sulfonatonaphthanlene; 4-acetamido-4-isothiocyanatostilbene-2,2′-disulfonic acid; pyrene-3-sulfonic acid; 2-toluidinonapththalene-6-sulfonate; N-phenyl, N-methyl 2-aminonaphthalene-6-sulfonate; ethidium bromide; stebrine; auromine-0,2-(9′-anthroyl)palmitate; dansyl phosphatidylethanolamin; N,N′-dioctadecyl oxacarbocycanine; N,N′-dihexyl oxacarbocyanine; merocyanine, 4-(3′-pyrenyl)butryate; d-3-aminodesoxy-equilenin; 12-(9′-anthroyl)stearate; 2-methylanthracene; 9-vinylanthracene; 2,2′-(vinylene-p-phenylene)bisbenzoxazole; p-bis[2-(4-methyl-5-phenyl oxazolyl)]benzene; 6-dimethylamino-1,2-benzophenzin; retinol; bis(3′-aminopyridinium)-1,10-decandiyl diiodide; sulfonaphthylhydrazone of hellibrienin; chlorotetracycline; N-(7-dimethylamino-4-methyl-2-oxo-3-chromenyl)maleimide; N-[p-(2-benzimidazolyl)phenyl]maleimide; N-(4-fluoranthyl)maleimide; bis(homovanillic acid); resazarin; 4-chloro-7-nitro-2,1,3-benzooxadizole; merocyanine 540; resorufin; rose bengal and 2,4-diphenyl-3(2H)-furanone. Preferably, the fluorescent detectable moiety is a fluorescein or rhodamine dye.

Another preferred detectable moiety is colloidal gold. The colloidal gold particle is typically 40 to 80 nm in diameter. The colloidal gold may be attached to a labeling compound in a variety of ways. In one embodiment, the linker moiety of the nucleic acid labeling compound terminates in a thiol group (—SH), and the thiol group is directly bound to colloidal gold through a dative bond. See Mirkin et al. Nature 1996, 382, 607-609. In another embodiment, it is attached indirectly, for instance through the interaction between colloidal gold conjugates of antibiotin and a biotinylated labeling compound. The detection of the gold labeled compound may be enhanced through the use of a silver enhancement method. See Danscher et al. J. Histotech 1993, 16, 201-207.

The term “effective amount” as used herein refers to an amount sufficient to induce a desired result.

Although generally used herein to define separate regions containing differing polymer sequences, the term “feature” generally refers to any element, e.g., region, structure or the like, on the surface of a substrate. Preferably, substrates will have small feature sizes, and consequently, high feature densities on substrate surfaces. For example, individual features will typically have at least one of a length or width dimension that is no greater than 100 microns, and preferably, no greater than 50 microns, and more preferably no greater than about 20 microns. Preferred embodiments of the present invention may have features as small as 1 micron, down to 0.5 microns. Thus, for embodiments employing substrates having a plurality of polymer sequences on their surfaces, each different polymer sequence will typically be substantially contained within a single feature.

The term “fragmentation” refers to the breaking of nucleic acid molecules into smaller nucleic acid fragments. In certain embodiments, the size of the fragments generated during fragmentation can be controlled such that the size of fragments is distributed about a certain predetermined nucleic acid length.

The term “genome” as used herein is all the genetic material in the chromosomes of an organism. DNA derived from the genetic material in the chromosomes of a particular organism is genomic DNA. A genomic library is a collection of clones made from a set of randomly generated overlapping DNA fragments representing the entire genome of an organism.

The term “hybridization” as used herein refers to the process in which two single-stranded polynucleotides bind non-covalently to form a stable double-stranded polynucleotide; triple-stranded hybridization is also theoretically possible. The resulting (usually) double-stranded polynucleotide is a “hybrid.” The proportion of the population of polynucleotides that forms stable hybrids is referred to herein as the “degree of hybridization.” Hybridizations are usually performed under stringent conditions, for example, at a salt concentration of no more than 1 M and a temperature of at least 25° C. For example, conditions of 5×SSPE (750 mM NaCl, 50 mM NaPhosphate, 5 mM EDTA, pH 7.4) and a temperature of 25-30° C. are suitable for allele-specific probe hybridizations. For stringent conditions, see, for example, Sambrook, Fritsche and Maniatis. “Molecular Cloning A laboratory Manual” 2^(nd) Ed. Cold Spring Harbor Press (1989) which is hereby incorporated by reference in its entirety for all purposes above.

The term “hybridization conditions” as used herein will typically include salt concentrations of less than about 1M, more usually less than about 500 mM and preferably less than about 200 mM. Hybridization temperatures can be as low as 5° C., but are typically greater than 22° C., more typically greater than about 30° C., and preferably in excess of about 37° C. Longer fragments may require higher hybridization temperatures for specific hybridization. As other factors may affect the stringency of hybridization, including base composition and length of the complementary strands, presence of organic solvents and extent of base mismatching, the combination of parameters is more important than the absolute measure of any one alone.

The term “hybridization probes” as used herein are oligonucleotides capable of binding in a base-specific manner to a complementary strand of nucleic acid. Such probes include peptide nucleic acids, as described in Nielsen et al., Science 254, 1497-1500 (1991), and other nucleic acid analogs and nucleic acid mimetics.

The term “hybridizing specifically to” as used herein refers to the binding, duplexing, or hybridizing of a molecule only to a particular nucleotide sequence or sequences under stringent conditions when that sequence is present in a complex mixture (for example, total cellular) DNA or RNA.

The term “isolated nucleic acid” as used herein means an object species invention that is the predominant species present (i.e., on a molar basis it is more abundant than any other individual species in the composition). Preferably, an isolated nucleic acid comprises at least about 50, 80 or 90% (on a molar basis) of all macromolecular species present. Most preferably, the object species is purified to essential homogeneity (contaminant species cannot be detected in the composition by conventional detection methods).

The term “ligand” as used herein refers to a molecule that is recognized by a particular receptor. The agent bound by or reacting with a receptor is called a “ligand,” a term which is definitionally meaningful only in terms of its counterpart receptor. The term “ligand” does not imply any particular molecular size or other structural or compositional feature other than that the substance in question is capable of binding or otherwise interacting with the receptor. Also, a ligand may serve either as the natural ligand to which the receptor binds, or as a functional analogue that may act as an agonist or antagonist. Examples of ligands that can be investigated by this invention include, but are not restricted to, agonists and antagonists for cell membrane receptors, toxins and venoms, viral epitopes, hormones (for example, opiates, steroids, etc.), hormone receptors, peptides, enzymes, enzyme substrates, substrate analogs, transition state analogs, cofactors, drugs, proteins, and antibodies.

The term “mRNA,” or sometimes referred to as “mRNA transcripts,” as used herein, includes, but not limited to pre-mRNA transcript(s), transcript processing intermediates, mature mRNA(s) ready for translation and transcripts of the gene or genes, or nucleic acids derived from the mRNA transcript(s). Transcript processing may include splicing, editing and degradation. As used herein, a nucleic acid derived from an mRNA transcript refers to a nucleic acid for whose synthesis the mRNA transcript or a subsequence thereof has ultimately served as a template. Thus, a cDNA reverse transcribed from an mRNA, an RNA transcribed from that cDNA, a DNA amplified from the cDNA, an RNA transcribed from the amplified DNA, etc., are all derived from the mRNA transcript and detection of such derived products is indicative of the presence and/or abundance of the original transcript in a sample. Thus, mRNA derived samples include, but are not limited to, mRNA transcripts of the gene or genes, cDNA reverse transcribed from the mRNA, cRNA transcribed from the cDNA, DNA amplified from the genes, RNA transcribed from amplified DNA, and the like.

The term “nucleic acid library” or sometimes refer by “array” as used herein refers to an intentionally created collection of nucleic acids which can be prepared either synthetically or biosynthetically and screened for biological activity in a variety of different formats (for example, libraries of soluble molecules; and libraries of oligos tethered to resin beads, silica chips, or other solid supports). Additionally, the term “array” is meant to include those libraries of nucleic acids which can be prepared by spotting nucleic acids of essentially any length (for example, from 1 to about 1000 nucleotide monomers in length) onto a substrate. The term “nucleic acid” as used herein refers to a polymeric form of nucleotides of any length, either ribonucleotides, deoxyribonucleotides or peptide nucleic acids (PNAs), that comprise purine and pyrimidine bases, or other natural, chemically or biochemically modified, non-natural, or derivatized nucleotide bases. The backbone of the polynucleotide can comprise sugars and phosphate groups, as may typically be found in RNA or DNA, or modified or substituted sugar or phosphate groups. A polynucleotide may comprise modified nucleotides, such as methylated nucleotides and nucleotide analogs. The sequence of nucleotides may be interrupted by non-nucleotide components. Thus the terms nucleoside, nucleotide, deoxynucleoside and deoxynucleotide generally include analogs such as those described herein. These analogs are those molecules having some structural features in common with a naturally occurring nucleoside or nucleotide such that when incorporated into a nucleic acid or oligonucleoside sequence, they allow hybridization with a naturally occurring nucleic acid sequence in solution. Typically, these analogs are derived from naturally occurring nucleosides and nucleotides by replacing and/or modifying the base, the ribose or the phosphodiester moiety. The changes can be tailor made to stabilize or destabilize hybrid formation or enhance the specificity of hybridization with a complementary nucleic acid sequence as desired.

The term “nucleic acids” as used herein may include any polymer or oligomer of pyrimidine and purine bases, preferably cytosine, thymine, and uracil, and adenine and guanine, respectively. See Albert L. Lehninger, PRINCIPLES OF BIOCHEMISTRY, at 793-800 (Worth Pub. 1982). Indeed, the present invention contemplates any deoxyribonucleotide, ribonucleotide or peptide nucleic acid component, and any chemical variants thereof, such as methylated, hydroxymethylated or glucosylated forms of these bases, and the like. The polymers or oligomers may be heterogeneous or homogeneous in composition, and may be isolated from naturally-occurring sources or may be artificially or synthetically produced. In addition, the nucleic acids may be DNA or RNA, or a mixture thereof, and may exist permanently or transitionally in single-stranded or double-stranded form, including homoduplex, heteroduplex, and hybrid states.

The term “polymorphism” as used herein refers to the occurrence of two or more genetically determined alternative sequences or alleles in a population. A polymorphic marker or site is the locus at which divergence occurs. Preferred markers have at least two alleles, each occurring at frequency of greater than 1%, and more preferably greater than 10% or 20% of a selected population. A polymorphism may comprise one or more base changes, an insertion, a repeat, or a deletion. A polymorphic locus may be as small as one base pair. Polymorphic markers include restriction fragment length polymorphisms, variable number of tandem repeats (VNTR's), hypervariable regions, minisatellites, dinucleotide repeats, trinucleotide repeats, tetranucleotide repeats, simple sequence repeats, and insertion elements such as Alu. The first identified allelic form is arbitrarily designated as the reference form and other allelic forms are designated as alternative or variant alleles. The allelic form occurring most frequently in a selected population is sometimes referred to as the wildtype form. Diploid organisms may be homozygous or heterozygous for allelic forms. A diallelic polymorphism has two forms. A triallelic polymorphism has three forms. Single nucleotide polymorphisms (SNPs) are included in polymorphisms.

The term “primer” as used herein refers to a single-stranded oligonucleotide capable of acting as a point of initiation for template-directed DNA synthesis under suitable conditions for example, buffer and temperature, in the presence of four different nucleoside triphosphates and an agent for polymerization, such as, for example, DNA or RNA polymerase or reverse transcriptase. The length of the primer, in any given case, depends on, for example, the intended use of the primer, and generally ranges from 15 to 30 nucleotides. However, longer primers are also preferred including from 80 to 160 nucleotides. Short primer molecules generally require cooler temperatures to form sufficiently stable hybrid complexes with the template. A primer need not reflect the exact sequence of the template but must be sufficiently complementary to hybridize with such template. The primer site is the area of the template to which a primer hybridizes. The primer pair is a set of primers including a 5′ upstream primer that hybridizes with the 5′ end of the sequence to be amplified and a 3′ downstream primer that hybridizes with the complement of the 3′ end of the sequence to be amplified.

The term “probe” is often used in the context of array technology as the polymer bound to the array. See U.S. Pat. No. 6,582,908 for an example of arrays having all possible combinations of probes with 10, 12, and more bases. Examples of probes that can be investigated by this invention include, but are not restricted to, agonists and antagonists for cell membrane receptors, toxins and venoms, viral epitopes, hormones (for example, opioid peptides, steroids, etc.), hormone receptors, peptides, enzymes, enzyme substrates, cofactors, drugs, lectins, sugars, oligonucleotides, nucleic acids, oligosaccharides, proteins, and monoclonal antibodies. As used herein, probes may be designed to be releasable, i.e., capable of being severed from the array and, thus, as interchangeable “primers.”

c) Massively Parallel Oligonucleotide Probe Synthesis and Purification

According to one aspect of the present invention, massively parallel oligonucleotide probe synthesis and purification is provided for applications that utilize large collections of defined high-fidelity oligonucleotides (e.g., from about 10¹ to about 10⁵ different sequences, generally between 25-160 bases in length) with or without authentic 3′-hydroxy termini. Preferably, the oligonucleotides are between about 80 to 160. It is also preferred that the oligonucleotides contain authentic 3′ hydroxyl groups. However, other types of 3′ hydroxyl groups are also preferred, such as phosphorylated.

In accordance with one aspect of the present invention, photolithographic synthetic strategies may provide a convenient approach to efficiently produce an array of such probes. In accordance with an aspect of the present invention, synthesis may be initiated with a reverse-orientation RNA monomer that contains an orthogonal 2′-OH group with an appropriate protective group. Two exemplary monomers are shown in FIG. 2. Following conventional 3′→5′ oligonucleotide synthesis, the 2′-OH protecting group is removed to allow base-induced intramolecular transesterification. The transesterification reaction causes release of the synthesized oligonucleotide, leaving an authentic 3′-hydroxy functionality, while the 2′,3′-cyclic phosphate remains attached to the solid support (see FIG. 1).

Accordingly, one embodiment of the present invention provides a method of fabricating a plurality of oligonucleotides having free 3′-hydroxyl groups from a high density oligonucleotide array, said method comprising the steps of

a) providing a solid substrate comprising a plurality of ribonucleotides attached thereto at a density, one said ribonucleotide shown below

wherein PG₁ is protecting group 1, PG₂ is protecting group 2, B is a naturally or non-naturally occurring base, and said ribonucleotide is attached to said substrate through the 5′-hydroxyl group; b) selectively removing PG₁ in pre-selected areas of the substrate to provide a plurality of free 3′-hydroxyl groups on said ribonucleotide; c) reacting said free 3′-hydroxyl groups with a 2′-deoxyribonucleotide having the structure

wherein PG₃ is protecting group 3 and RG is a reactive group to couple said 2′-deoxyribonucleotide to said ribonucleotide to provide the structure

d) selectively removing PG₃ from the 5′-hydroxyl of said 2′-deoxyribonucleotide in pre-selected areas to provide a plurality of free 5′-hydroxyl groups; e) reacting said free 5′-hydroxyl groups with an additional 2′-deoxyribonucleotide having the structure

to yield a product of the structure

f) repeating steps d and e one or more times to provide said oligonucleotides attached to said solid substrate; g) removing PG₂ from one or more of said ribonucleotides to provide a free 2′-hydroxyl group on each of said one or more ribonucleotides; and h) transesterifying each of said one or more ribonucleotides to yield said solid substrate having a cyclic ester attached thereto and free oligonucleotides, each oligonucleotide having a 3′-hydroxyl group and having the structure

In certain aspects of the present invention the 2′-deoxyribonucleotide has a phosphoramidite reactive group as shown by

wherein R₁ is selected from cyanoethyl, methyl, t-butyl, trimethylsilyl or the like, and R₂ and R₃ are independently selected from isopropyl, cyclohexyl or the like.

In certain aspects of the present invention the oligonucleotides are probes while in other aspects of the present invention the oligonucleotides are primers.

In one aspect of the present invention, PG₁, PG₃ and PG₄ are independently selected protecting groups. These protecting groups may be the same as or different from one another. It has been discovered in accordance with the present invention that to achieve suitable primer purity and quantity, a highly-efficient photogroup (>90% average stepwise coupling efficiency) is preferred for PG₁, PG₃ and PG₄, such as NPPOC or MBPMOC:

Both NNPOC and MBPMOC give greater than 90% stepwise coupling. For example NNPOC gives 97-98% stepwise coupling.

Alternatively, DMT-based chemistry could be employed in conjunction with photoacid. DMT-based resist methodologies have been found, in accordance with the present invention to provide up to a 99% stepwise yield. In certain embodiments of the present invention, when PG₁, PG₃ or PG₄ are DMT, the DMT group may be removed in selected areas by exposure to acid generated by a photoacid generator in the presence of electro magnetic radiation of an appropriate wavelength in the presence of an acid scavenger. In further embodiments of the present invention the acid scavenger is selected from the group consisting of organic bases and polymeric bases. In preferred aspects of the present invention, the acid scavenger is a polymeric base.

In another aspect of the present invention, it is further contemplated that combinations of DMT-based and photochemical-based probe assembly could be performed, for example to assemble common regions of the probe sequence. Despite the specific primer array synthesis methodology, high-density substrates (200-2000 pmoles/cm²) can be employed to significantly boost primer yield. Such substrates are typically based upon three-dimensional architectures, thin-films or polymeric coatings.

The rate of transesterification (i.e., oligonucleotide release) can be significantly enhanced by raising the pH of the aqueous solution (pH 9-12) and/or by the addition of particular metal ions, which are known in the art to facilitate or catalyze such reactions.

Exemplary 2′-OH RNA monomer protecting groups, PG₂, are Ac (removed during base deprotection), FPMP or CEE (removed with mild acid, but not strong acid), TBDMS or TOM (removed with fluoride ions) or even a photogroup that is active at wavelengths longer than 365 nm.

In preferred embodiments of the present invention PG₂ will be orthogonal to PG₁, PG₃, and PG₄. As such, the conditions used to deprotect PG₂ are different than those used to deprotect PG₁, PG₃ and PG₄. For example, if acid labile protecting groups are used for PG₁, PG₃ and PG₄, then PG₂ may be protected with a photolabile protecting group. The converse is also true, i.e., if photolabile protecting groups are used for PG₁, PG₃ and PG₄, then PG₂ may be protected with an acid labile protecting group. In some embodiments, photo labile protecting groups can be used for all of PG₁, PG₂, PG₃ and PG₄, provided that the photo labile protecting group of PG₂ is active at wavelengths longer than those of the photo labile protecting group of PG₁, PG₃ and PG₄, e.g., longer than 365 nm.

Because the coupling reactions between the free 5′-hydroxyl groups and the reactive group of the 2′-deoxyribonucleotide typically are not 100% efficient in a finite time period, a small percentage of truncated sequences, i.e., sequences which did not undergo the expected coupling event, is produced at each coupling step. To prevent these truncated sequences from undergoing further coupling reactions to produce unexpected oligonucleotide sequences, the unreacted free 5′-hydroxyl group can be capped prior to performing additional coupling reactions to render it unreactive for subsequent synthesis steps. This capping reaction may be accomplished by acetylation using methods known in the art.

In another aspect of the present invention, steps are employed to enrich or purify the full-length oligonucleotides (e.g., probes or primers). For example, if a base-stable RNA monomer is employed, the final 5′-DMT group is retained on the probe and the array is deprotected in the usual manner. The deprotection step removes the DNA protecting groups, reverses some unwanted chemical modifications, and also cleaves depurinated sites. The protecting groups and truncated fragments are washed away from the solid support, leaving behind the immobilized full-length probes that contain a 5′-DMT group as well as immobilized truncated species that do not possess a 5′-DMT group.

A subsequent processing step causes removal of the 2′-OH RNA protecting group and subsequent transesterification/release of probes (FIG. 3). The solution containing the mixture of free oligonucleotides can then be adsorbed onto a disposable hydrophobic oligonucleotide purification cartridge (e.g., Waters Sep-Pak, ABI OPC, etc.) to isolate only those oligonucleotide species that possess a 5′-DMT group.

Accordingly, the present invention provides a method of purifying a set of oligonucleotides, comprising the steps of

a) providing a solid substrate comprising a plurality of ribonucleotides attached thereto at a density, one said ribonucleotide shown below

wherein PG₁ is protecting group 1, PG₂ is an alkalai resistant protecting group, B is a naturally or non-naturally occurring base, and said ribonucleotide is attached to said substrate through the 5′-hydroxyl group; b) selectively removing PG₁ in pre-selected areas of the substrate to provide a plurality of free 3′-hydroxyl groups on said ribonucleotide; c) reacting said free 3′-hydroxyl groups with a 2′-deoxyribonucleotide having the structure

wherein PG₃ is DMT, B is a naturally or non-naturally occurring base in which the exocyclic amine groups are protected with alkalai labile protecting groups, and RG is a reactive group to couple said 2′-deoxyribonucleotide to said ribonucleotide to provide the structure

d) selectively removing PG₃ from the 5′-hydroxyl of said 2′-deoxyribonucleotide in pre-selected areas to provide a plurality of free 5′-hydroxyl groups; e) reacting said free 5′-hydroxyl groups with an additional 2′-deoxyribonucleotide having the structure

wherein PG₄ is DMT, to yield a product of the structure

f) repeating steps d and e one or more times to provide said oligonucleotides attached to said solid substrate; g) deprotecting said set of oligonucleotides while said oligonucleotides are still attached to said substrate by subjecting said oligonucleotides to alkaline conditions, wherein said alkaline conditions remove said alkalai labile protecting groups acting to protect said exocyclic amines and in addition cleave depurinated DNA, leaving a 3′-end of the cleaved depurinated strand attached to the substrate and releasing a truncated fragment; h) washing the solid support to remove said released truncated fragments and protecting groups, leaving full length oligonucleotides having a DMT group on the 5′-hydroxyl group and truncated oligonucleotides without the 5′-DMT group; i) removing PG₂ from one or more of said ribonucleotides to provide a free 2′-hydroxyl group on each of said one or more ribonucleotides; j) transesterifying each of said one or more ribonucleotides to yield said solid substrate having a cyclic ester attached thereto and a mixture of full length oligonucleotides having 5′-DMT groups and free 3′-hydroxyl groups and having the structure

and truncated fragments lacking the DMT group; k) applying the mixture to hydrophobic oligonucleotide purification resin to isolate only those oligonucleotides having the 5′-DMT group to yield full length oligonucleotides; and l) removing the 5′-DMT group to provide full length oligonucleotides having both 5′- and 3′-hydroxyl groups.

As an alternative to the procedure described above, the 2′-OH RNA protecting group is simply Ac, which is removed along with the other protecting groups during standard deprotection. If the non-catalyzed transesterification rate is low, then full-length oligonucleotides will not be substantially released until the reaction conditions are appropriately adjusted to cause transesterification.

It is contemplated that reporter groups (e.g., chromophores, fluoraphores, detectable labels) or affinity tags (e.g., biotin) can be incorporated into the probe sequences, in either single-color or multi-color formats. Phosphorylation at either terminus (or both termini) is also possible. Dual-labeled oligonucleotide “probes” (e.g., TaqMan probes and molecular beacons) are also contemplated in accordance with the instant invention. Additionally, non-conventional building blocks (e.g., nucleoside analogues or mimics) could be incorporated into the probe/primer, either in part or in whole. Primer quantity will be a function of the stepwise coupling yield, primer length, the surface loading, feature size and feature redundancy of a given array design. The relative concentration of each probe/primer can be adjusted by controlling the redundancy of the array design.

It should be noted that many of the embodiments described herein are described with reference to the fabrication of oligonucleotide probes and/or primers. However, these descriptive embodiments are not intended to limit the types of or uses for oligonucleotides which can be produced and purified or isolated using the described methods. The oligonucleotides produced by the described methods can have any desired sequence composition and be utilized in any context in which oligonucleotides of defined sequence are desired. Oligonucleotides can be prepared according to the methods of the invention singly or in sets within the larger population of distinct sequences. By way of non-limiting example, forward and reverse PCR primers for a particular target sequence may be synthesized as a set on the array; alternatively, sets of probes or primers differing by a single base at specific positions can be produced.

A preferred aspect of the present invention is that synthesis is initiated with a reverse-orientation RNA monomer that contains an orthogonal 2′-OH protecting group. Following conventional 3′→5′ probe synthesis, the 2′-OH protecting group is removed to allow base-induced intramolecular transesterification. The transesterification reaction causes release of the synthesized probe with an authentic 3′-hydroxy functionality, while the 2′,3′-cyclic phosphate remains attached to the solid support (see FIG. 1). The rate of transesterification (i.e., probe release) can be significantly enhanced by raising the pH of the aqueous solution (pH 9-12) and/or by the addition of particular metal ions, which are known in the art to facilitate or catalyze such reactions.

Two exemplary monomers are depicted in FIG. 2: Exemplary 2′-OH RNA monomer protecting groups are Ac (removed during base deprotection), FPMP or CEE (removed with mild acid, but not strong acid), TBDMS or TOM (removed with fluoride ions) or even a photogroup that is active at wavelengths longer than 365 nm.

Another preferred aspect of the present invention is the steps that are employed to enrich or purify the full-length probes (see FIG. 3). For example, if a base-stable RNA monomer is employed, the final 5′-DMT group is retained on the probe and the array is deprotected in the usual manner. The deprotection step removes the DNA protecting groups, reverses some unwanted chemical modifications, and also cleaves depurinated sites. The protecting groups and truncated fragments are washed away from the solid support, leaving behind the immobilized full-length probes that contain a 5′-DMT group as well as truncated species that do not possess a 5′-DMT group. A subsequent processing step causes removal of the 2′-OH RNA protecting group and subsequent transesterification/release of probes. The solution containing the mixture of probes can then be adsorbed onto a disposable hydrophobic oligonucleotide purification cartridge (e.g., Waters Sep-Pak, ABI OPC, etc.) to isolate only those probe species that possess a 5′-DMT group.

As an alternative to the procedure described above, the 2′-OH RNA protecting group is simply Ac, which is removed along with the other protecting groups during standard deprotection. If the non-catalyzed transesterification rate is low, then full-length probes will not be substantially released until the reaction conditions are appropriately adjusted to cause transesterification.

It is contemplated that reporter groups (e.g., cluomophores, fluorophores, detectable labels) or affinity tags (e.g., biotin) can be incorporated into the probe sequences, in either single-color or multi-color formats. Phosphorylation at either terminus (or both ternlini) is also possible. Dual-labeled oligonucleotide “probes” (e.g., TaqMan probes and molecular beacons) are also contemplated. Additionally, non-conventional building blocks (e.g., nucleoside analogues or mimics) could be incorporated into the probe/primer, either in part or in whole. Primer quantity will be a function of the stepwise coupling yield, primer length, the surface loading, feature size and feature redundancy of a given array design. The relative concentration of each primer can be adjusted by controlling the redundancy of the array design.

In accordance with an aspect of the present invention, a method for massively parallel oligonucleotide probe synthesis and release of said oligonucleotides from an array of probes on a solid substrate is provided, the method having the steps of providing a solid substrate;

attaching a plurality of linkers to the substrate, each said linker comprising a cleavable moiety, wherein said cleavable moiety is activatable only at a distinct set of conditions and wherein activation of said cleavable moiety disrupts the linker to allow of a polymer bound to said linker, to provide a substrate with a plurality of attached linkers; attaching a first monomer to at least one of said plurality of attached linkers to provide an attached first monomer; attaching a second monomer to a least one of said attached first monomers or said plurality of attached linkers to provide an attached second monomer; attaching a third monomer to a least one of said attached first monomer, said second monomer or said plurality of attached linkers to provide an attached third monomer; repeating said steps of attaching monomers until the desired array of polymers is complete; and subjecting the array to the distinct set of conditions to release polymers from said array.

In a preferred embodiment of the present invention, the desired array has between 10¹ to 10⁵ oligonucleotides of different sequences which are between about 80-160 bases in length.

According to another aspect of the present invention, it is preferred that said released oligonucleotides have authentic 3′-hydroxy termini upon exposure to said distinct set of conditions or are further processed to have authentic 3′ hydroxyl termini.

According to another aspect of the present invention, it is preferred that the method further comprising the use of the photoprotective groups, preferably NPPOC or NNPOC to provide suitable primer purity and quantity.

According to another aspect of the present invention, it is preferred that the method employ DMT-based photoresist groups to provide suitable primer purity and quantity.

According to another aspect of the present invention, it is preferred that ink jet based in situ oligonucleotide synthesis is used to provide the oligonucleotide probes.

According to another aspect of the present invention, it is preferred that the method is initiated with a reverse-orientation RNA monomer that contains an orthogonal 2′-OH protecting group.

According to another aspect of the present invention, it is preferred that following conventional 3′→5′ probe synthesis, the 2′-OH protecting group is removed to allow base-induced intramolecular transesterification. Base-induced intramolecular transesterification is preferentially performed by raising the pH of the aqueous solution to pH 9-12 or by the addition of particular metal ions.

All patents, patent applications, and literature cited in the specification are hereby incorporated by reference in their entirety. In the case of any inconsistencies, the present disclosure, including any definitions therein will prevail.

The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention. 

1. A method of synthesizing one or more oligonucleotides on a solid substrate, wherein the method comprises: attaching to a solid substrate one or more ribonucleotides having the following structure:

wherein PG₁ is a first protecting group, PG₂ is a second protecting group, B is a base, and the one or more ribonucleotides are attached to the substrate through 5′ hydroxyl groups; removing PG₁; synthesizing the one or more oligonucleotides by sequential addition of one or more additional nucleotides to a 3′ hydroxyl group of the one or more ribonucleotides, thereby synthesizing one or more oligonucleotides on a substrate.
 2. The method according to claim 1, which further comprises transesterifying the one or more oligonucleotides synthesized on the solid substrate, thereby releasing the one or more oligonucleotides form the solid substrate.
 3. The method according to claim 1, wherein the one or more oligonucleotides comprises sequences complimentary to an individual genomic library.
 4. The method according to claim 3, wherein the one or more oligonucleotides are synthesized by a combinatorial synthesis strategy.
 5. The method according to claim 3, wherein the individual is selected from the group consisting of: mammals, plants, and bacteria.
 6. The method according to claim 5, wherein the individual is human.
 7. The method according to claim 3, wherein the one or more oligonucleotides are between 80 and 160 nucleotides in length.
 8. The method according to claim 6, wherein sequences of the one or more oligonucleotides are complimentary to mRNA sequences in the genomic library.
 9. The method according to claim 1, wherein synthesizing the one or more oligonucleotide by sequential addition of one or more additional nucleotides is accomplished by photolithography.
 10. The method according to claim 1, wherein the substrate is glass.
 11. The method according to claim 2, which further comprises attaching biotin to the one or more oligonucleotides.
 12. The method according to claim 11, wherein attaching biotin to the one or more oligonucleotides occurs after transesterification. 